Polymeric material



Patented MarlZ, 1943 UNITED STATES, PATENT OFFICE '2,a12,sss I V TPOLYMERIC MATERIAL William E. Hanfdrd, Wilmington, DeL, assignor;

to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporationof Delaware No Drawing. Application April 1, 1940,

Serial No. 327,324 r V 7 Claims. (01.260-78) This invention relates topolymeric materials and more particularly to new' polyamides.

In U. S. Patent 2,071,253 are described a number of polyamides derivedfrom the polymerization of amino acids and their amide-formingderivatives. These polyamides have high molecular weights, are extremelystrong, and can be formed into useful fibers. For such uses as coatingcompositions and films, howeventhese polyamides have the disadvantagethat they are insoluble in common organic solvents, being soluble onlyin such materials as phenols and formic acid, and absorb fairly largeamounts of water.

This invention has as an object the preparation of new and usefulpolymeric materials. A further object is the preparation of polyamidesof special utility in the preparation .of coating comatoms andpreferably R is a hydrocarbon radical However, R 1 and containingfrom 7to 12atoms. R may be heteroatomic radicals containing oxygen, sulfur, ornitrogen in addition to carbon. It will ;be observed that the minimumradical length of the amino acid is 7, wherein iadical,

length" refers tothe number of atoms in the positions and films. Otherobjectswill appear hereinafter.

The above objects are accomplishedby heating at amide-formingtemperatures a polymerforming composition comprising an acyclicmonoaminomonocarboxylic acid which contains a chain of at least 16atoms, 'has'its amino group attached to a secondary carbon atom, and hasat least five atoms separating the amino and carboxyl groups. It is tobe understood that mention herein of an amino acid is intended toinclude also its amide-forming derivatives, such as' in which is adivalent organic radical having a chain length of at least 4, R is amonovalent organic radical, and R'-C-R-C, which repre-' sents the chainlength of the acid, has at least 16 atoms in the chain. Preferably R isa hydrocarbon radical containing from 5 to 9 carbon carboxyl group andthe nitrogen of the amino group. In terms of the above formula, theradical length is represented by the number of atoms. 7

in the chain N-'CRC. The preferred acids have radical lengths'of 10 to15. Thus 12-am1- acids, the preferred polyamidesare those derived frompolymer-forming compositions containing in addition to an amino acid ofthe above type other polyamide-forming reactants, and particularly amixture of diamine and dibasic acids which is preferably used in theform of the diamine-dibasic acid salt. These polyamides, which can bereferred to as interpolyamides, are preferred because they aremoreflexible, in general have a higher melting point, and can usually beprepared more economically. i 1

The term "polyamide as used herein includes not only the polymers whichare obtainedsolely' from the above mentioned amino acids or frommixtures of the above mentioned amino acids with other polyamide-formingcompositions, but

of this invention yield thehydrochloride of the amino acid used in theirpreparation. 7

In the usual procedure for carrying out the invention the amino acid,with or without other i closed reaction vessel at polymerizingtemperatures until a low molecular weight polyamide is" formed. Thetemperatures employed are between about 120 and 300? C.,. and in mostinstances between 200 and 285 C. The optimum temperature and time ofreaction vary with the nature of the reactants and the proportions inwhich they occur and also vary with the softening point of thepolymerized product. In order to produce a high molecular weightpolyamide, f

which is desired for most purposes, the heating is continued atpolymerizing temperatures under conditions which permit the removal oftheliberated water, alcohol, ammonia or other secondary product atatmospheric or reduced pressure. Formation of a high molecular weightproduct is evidenced by the fact that the polymer is tough and can beformed into films or into pliable filaments.

viscosity of at least 0.4, where intrinsic viscosity is defined as inPatent 2,130,948. The entire process is desirably carried outin theabsence of oxygen which can be done, for example, by op- The highmolecular stage is not in 'general reached until the polymer has anintrinsic erating in the presence of an-lnert gas, such as p nitrogen orcarbon dioxide, or by operating under reduced pressure. V r r Thefollowing examples, in which the quantities of reagents are parts byweight, are presented to illustrate in greater detail the processes ofthis invention. Examples I-lII illustrate the preparation of polyamidesfrom the amino acids alone,

polymer-forming ingredients, is heated in a Example IV Equal parts of amixture of 9- and 10-aminostearic acid and ofhexamethylenediamine-adipic acid salt were heated together in a sealedreaction vessel at 200210 C. for 3 hours. The resulting low molecularweight polyamide was then heated at atmospheric pressure in anatmosphere of nitrogen for 1.5 hours at285 C. Polymerization wascompleted by heating for 3 hours at 285 7 C. at a pressure of 5-15 mm.The polyamide softened at 147 C., had an intrinsic viscosity of 0.6, andcould be spun and cold-drawn. It was soluble in the lower aliphaticalcohols and in alcohol-aromatic hydrocarbon mixtures.

' Example V Equal parts of 12-aminostearlc acid andhexamethylenediamine-adipic acid salt were placed in a stainless steelautoclave. The temperature of. the reaction mixture was held at 210-230C. for

-3.5 hours, the pressure rising from atmospheric to 250 lbs/sq. in. Thewater formed in the reaction was then removed during hour, by slowlyreducing the pressure to atmospheric, the'tem- 'perature of the reactionmixture dropping to about 200C, Heating was continued under 5 mm.pressure for an additional 3.5 hours at a temperature of 250-260 C. Thematerial thus obtained had a softening point of 168 C., an intrinsicviscosity of 0.99, and a tensile strength of 6,500 lbs/sq. It wasspinnable into filaments which could be cold-drawn. The material waswhereas th remaining examplesand the table,

following the examples illustrate the preparation of the more preferredproducts of this invention, 1. e. the inter polyamides.

Example I .1

12-aminostearic acid was heated in a sealed pressure vessel at 210-230C(ior 16 hours. The low molecular weight polyamide thus formed was thenheated at 5-15 mm. pressure at 255 C. for

' 15 hours. The resulting polymer softened at 109 C., had an intrinsicviscosity of'0.63,'and could be spun into fibers. The material wassoluble in the ance to heat embrittlement.

lower alcohols such as ethanol andv the butanols and in alcohol-aromatichydrocarbon mixtures.

It could be hot-pressed .or solvent-cast to give films of exceptionalpliability; toughness, and elasticity. Samples of these films absorbedless than 0.5% water at 100% R. H.- (relative humidity). In contrast th"polymer of 17-amino-heptadecanoic acid, a long chain amino" acid inwhich the amino group is attached to a primary carbon atom, is insolublein the above mentioned solvents and absorbs twice as much water at 100%R. H.

Example I] Methyl 12-aminostear-ate was heated at 200 C. in asealed tubefor 3.5 hours. Heating was then continued at 1 mm; pressure for 2 hoursat'200- V C. and for an additional 3 hours at 255 C. The

resulting polymer was spun from melt into pliable filaments; Thefilaments could be cold drawn.

Example III A mixture of 9- and 10-aminostearic acid was heatedat 255 C.for 20 hoursat 3-4 mm. pressure. The polymer softened at 110? 0., had anintrinsic viscosity of 0.73 and could be formed into fibers and films.It was soluble in hot ethanol and in chloroform-methanol mixtures, andsomewhat soluble in hot toluene.

soluble in chloroform-methanol mixtures andin furfuryl alcohol.Hot-pressed or solvent-cast films showed exceptional toughness andresist- Water absorption was less than 4% at 100% R. H. The polyamidederived from hexamethylenediamine and adipic acid aloneabsorbs about 8%moisture at 100% Example VI A mixture of equal parts of 12-aminostearicacid and hexamethylenediamine-sebacic acid salt was heated in a sealedpressure vessel for 2 hours at 210 0.. The lowmolecular weight polyamidethus obtained was then heated in an atmosphere Example VII 9 A mixtureof 10 parts l2-aminostearic'acid, 6 parts e-caprolactam, and 9 partshexamethylenediamine-adipic acid salt was heated in a sealed tube at 210C. for 1 hour and thanat 255 C. for 17 hours. Heating was continued at apressure of 2 mm. at 255 C. for 3 hours. The polymer thus obtainedhad asoftening'point of 118-120 C. and an intrinsic viscosity of 0.99. Thematerial was tough and spinnable and had a water absorption of less than8% at 100% R. H. The polyamide comprised of 9 parts hexamethylenediamineadipic acid and 6 part e-caprolactam absorbs about 13% moisture at 100%R. H.

Additional examples of interpolyamides de- 'l2-aminostearic acid (15),hexarived from 12-aminostearic acid are listed in the following table:

lz-aminostecr ic acid interpolyamides 1 Percent water Sottgn- Inmmabsorption sic vispgg t.

cosity Composition (parts by weight of reactants) at 507 at 100 11.11?an? lz-aminostearic acid (90), hexamethylenediamine-adipic acid salt(10) l2 aminostearic acid (75), hexametbylenediamine-adipic acid salt(25) l2-aminostcaric acid (60)- hexamethylenediamine-adipic acid salt(40) IZ-aminostearic acid (40), hexamethylanediamine-adipic acid salt(60) maminostearic acid (5), hexamethylenediamine-adipic acid ""f". "5""l2-ammostear1c acid (50), p-bis(2- aminoethyl)benzene-sebacic acid salt(50) l2-aminostearic acid (40), caprolactam (60) merh lenediamine'adipicacid sag Z45), e-aminocaproic acid l2-aminostearic acid (30),hexamethylenediamine-adipic acid salt (25), hexamethylenediamine-sebacicacid salt (45) lZ-aminostearic acid (15),hexamethylenediamine-sebacicacid sgt (55), G-aminocaproic acidlz-aminostearic acid (30), hexamethylenediamine-adipic acid salt (45),hexamethylenediamine-sebacic acid salt (15), 6- aminocaproic acid (10)-;175

1 The dashes in the table indi itethat no measurement was made.

The preferred interpolymers are obtained by reacting the above describedlong chain amino acids with other bifunctional reactants, as forinstance those disclosed in U. S. Patent.2,07l,250. Particularlyvaluable for thiscpurpose .are other polyamideforming reactants which,as indicated in the foregoing table, may be either those of the aminoacid type described in U. S. Patent 2,071,253 or those ,of theydiamine-dibasic acid type described in U. S. Patent 2,130,948.Additional bifunctional reactants useful in the preparation of thelinear interpolymers include hydroxy acids and alkanolamine-dibasic acidsysterns. The polyamides of this invention are, however, also desirablymodified for some purposes by including in the reaction mixture fromwhich the polymers are prepared such materials as pigments, plasticizersor resinous materials, e. g. phenol-formaldehyde resins. To preventincrease in molecular weight with consequent undesirable increase inviscosity during melt spinning of filaments it is desirable to includewith the reactants from which the polyamides are prepared a. viscositystabilizing agent, as for instance a, small amount of acetic orpropionic acid or similar amide-forming reactant.

Although the preferred embodiment comprises.

heating the reactants until they have a' sufiiciently high molecularweight to exhibit good filmforming properties, it is within the scope ofthis invention to discontinue heating before this stage. The lowmolecular weight polymers are useful for certain applications, e. g. infinely divided form for use as carriers for dyes in making organicpigments.

In addition to the several above-mentioned amino-stearic acids, theproducts of this invention may be obtained with other amino acids whichcomply with the requirements previously specified. Examples of suchacids, in which the chain. may be composed entirely of carbon or i maybe-heteroatomic, are as follows: g cmwnoromcmhc00H V Q-aminopalmiticacid CHs(CHz)a(|lH(CHa)1C O OH NR2 Q-aminostaric acid cmwanr-omcncncoonNH1 7 9-amino-5-oxatrico-sanoic acid omwnmswnoPomomnoo on NHz 10amin0-l5-thioocta-decanoic acid v I The polyamides of this invention canbe formed into films and fibers possessing marked toughness andelascity. These polyamides are further characterized by their goodsolubility in organic solvents and by their low water absorption. Forinstance, they are soluble in such solvents as ethanol, butanol, andalcohol-aromatic hydrocarbon mixtures, in which the previously knownamino acid polyamides, including those obtained from the long chainomega amino acids. are insoluble. combination of desirable propertiespossessed by the polyamides of this invention has not been obtainedbefore in polyamides of the amino acid type.

molding, coating, impregnating, and adhesive compositions. exceptionalresistance to abrasion and heat embrittlement make these pc'lyamidesparticularly valuable for use as electrical insulation composltions.Other uses are as bristles, rods, tubes, ribbons, wrapping films, and asa photographic film base. When these particles are made from the moltenpolymer it is desirable to effect rapid chilling of-the articles duringtheir formation, I e. g. by exposure to a cool surface or by quenchingwith a non-solvent for the polyamide, e. g. water. The extreme waterinsensitivity and good solubility of the present polyamide's makepossible their use in various types of waterproof coatings byapplication as a clear lacquer or pigmented enamel. The polymers mayalso be applied from melt as coatings on fabrics, paper, metal, andother surfaces. In the above and in The present products are usefulgenerally as ingredients in j The low water absorption and low meltingpoint, high melting polyarnides modified by preparation in the presenceof a small amount of such an amino acid have'better melt spinningproperties thanthe unmodified high melting polyamide' Thus the polyamideprepared by polymerizing hexamethylenediamineadipic acid salt in thepresence'of 1 to 5% of weight of IZ-aminostearic acid can be spun frommelt into high tenacity yarn at a faster rate than unmodifiedpolyhexamethylene adipamide. This improvement is believed to beassociated with the fact that the modified polyamide is less crystallinethan the unmodified polyamide or at least has less tendency tocrystallize on cooling from the melt. For the same reason the modifiedpolyhexamethylene adipamide is more read-- ily obtained. inthe form of'transparent films than the unmodified polymer.

As many apparently widelyfl different embodiments of this invention maybe made without departing from the spirit and scope thereof, it is -tobe understood that I do not limit myself to the specific embodimentthereof except as defined in the appended claims. It should beunderstood, however, that the mention of acid in the appended. claimsincludes also amideforming derivatives of the acid.

I claim:

1. A process for making polyamides which comprises reacting by heatingunder amide forming conditions different polyamide-forming compositionsone of which is a mixture of a diamine and a dicarboxylic acid andanother of which .is an acyclic monoaminomonocarboxylic acid of theformula wherein R is a hydrocarbon radical containing 7.

to 12 atoms, R is a hydrocarbon radical containing 5 to 9 carbon atoms,and R'-CRC has achain length of at least 16 atoms, and continuing thereactionnnder said conditions until the polymer obtainedcan be spun intofilaments which can be cold drawna V a 2. An interpolyamide comprisingthe reaction product of different polyamide-forming compositions one ofwhich is a mixture of a diamine and a dicarboxylic acid and another ofwhich is an acyclic monoaminomonocarboxylic acid of the formula 1wherein R is a hydrocarbon radical containing 7 to 12 atoms, R. is ahydrocarbon radical containing 5 to 9 carbon atoms and R'CRC has .achain length of at least 16 atoms.

3. An interpolyamide comprising the reaction product of different.polyamide-forming compositrons one of which is a mixtureof a diamineand a dicarboxylic acid and another of which is an aminostearic acidwherein the amino group is stearic acid and a diamine-dibasic acidmixture and in which the 12-aminostearic acidis present in amount from1% to said interpolyamide having a softening point substantially higherthan'the polyamide obtained from said 12-aminostearic acid alone. 7 l

5. 'A coating composition comprising the interpolyamide defined in claim2.

6. A filament comprising the interpolyamide defined in claim 2.

7. A self-supporting film comprising the interpolyamide defined in claim2.

' WILLIAM E. HANFORD.

